Conventionally, a non-contact type torque sensor that detects a steering torque acting on a steering shaft via a magnetic force is used as a torque sensor disposed in a steering device of a vehicle.
Torque sensors disclosed in JP2007-240496A and JP2007-292550A, published by the Japan Patent Office in 2007, both comprise a torsion bar accommodated in a housing to be capable of rotating, an input shaft and an output shaft coupled to respective ends of the torsion bar, a magnetism generating portion constituted by a multipolar magnet fixed to the input shaft, a rotating magnetic circuit portion constituted by a multipolar yoke fixed to the output shaft, a fixed magnetic circuit portion fixed to the housing, and a magnetic sensor that detects a magnetic flux density led to the fixed magnetic circuit portion. The magnetism generating portion is constituted by a back yoke formed from a yoke fixed to the input shaft and a ring magnet formed from a multipolar magnet fixed to the back yoke via an adhesive.
When a torque acts on the torsion bar such that the torsion bar undergoes torsional deformation, relative positions of the magnetism generating portion and the rotating magnetic circuit portion in a rotation direction vary. In accordance with the torsional deformation, the magnetic flux density that is led to the fixed magnetic circuit portion from the magnetism generating portion via the rotating magnetic circuit portion varies. The magnetic sensor outputs a signal corresponding to the magnetic flux density. The torque acting on the torsion bar is detected on the basis of the signal output from the magnetic sensor.